1. Field of the Invention
The present invention relates to information terminals and cartographic information providing systems and, more specifically, an information terminal and a cartographic information providing system for carrying out map display, position detection, route search, and route guidance by using digital cartographic data.
2. Description of the Background Art
(First Conventional Art)
In recent years, vehicles with a navigation system mounted thereon have been prevalent. Such conventional navigation system includes a map storage device having a read-only large-capacity storage medium, such as CD-ROM and DVD-ROM. A terminal for achieving this navigation system is implemented by a terminal dedicated to the navigation system, a general-purpose information processing device such as a PDA (Personal Digital Assistant), or other devices. The storage medium previously stores cartographic data for presentation to users. The storage device reads the cartographic data stored in the storage medium as required. The read digital cartographic data is used for route search or correction of a current position (map matching). To carry out these processes, the cartographic data contains road network data including at least connection information indicating how nodes and links are connected to one another. Here, each node indicates an intersection located on a road network, and each link indicates a vector representing a road located between two intersections (nodes) . The nodes and the links are connected to one another, and information about how they are connected is included in the road network data. Based on the road network data including a collection of the nodes, the links, and the connection information, the road network is presented on a map.
The nodes, the links, and the connection information are enough for representing a minimum required road network, but not enough for displaying a map. For example, roads on mountain or seashore ranges are often curved between intersections. To display the curved shapes of the roads, the road network data further includes information for specifying the shapes of the links.
Furthermore, to classify the roads by types, such as national highways, local roads, the number of lines, and the presence or absence of central reserves, the road network data further includes attribute information indicating the types of roads, etc.
Some intersections are provided with names, and some are not. Furthermore, some intersections have a traffic signal and some do not. Therefore, the road network data further includes attribution information for each node. The attribution information for each node contains a name of the intersection corresponding to the relevant node, the presence or absence of a traffic signal, etc.
(Second Conventional Art)
As described in the above first conventional art, the conventional navigation system can use only the cartographic data recorded on the read-only storage medium, and therefore can hardly provide real-time information. Such real-time information is typified by, for example, traffic information and weather information. Japanese Patent Laid-Open Publication No. 7-262493 (1995-262493) discloses a map providing system capable of providing real-time information and cartographic data. In this map providing system, real-time information and cartographic data are downloaded from an information providing center (center station) through a communications medium to a vehicle-mounted terminal. Furthermore, to achieve the above navigation system, a terminal having a small data storage capacity, such as a general-purpose information processing device (PDA, cell phone terminal, etc.) , may be used for downloading the cartographic data from the center station.
The above map providing system is constructed based on mobile terminal communications technologies and digital broadcast technologies for providing various information on a real-time basis. In the above constructed map providing system, the center station distributes information to the mobile terminal located within a service area by using a predetermined broadcast channel. The center station is typified by a communications satellite (CS), a broadcast satellite (BS), or a ground-wave digital broadcast station. An example map providing system using these mobile terminal communications technologies and digital broadcast technologies is disclosed in Japanese Patent Laid-Open Publication No. 7-154350 (1995-154350), wherein a technique for limiting a broadcast area capable of receiving specific information is disclosed.
In the map providing system disclosed in Japanese Patent Laid-Open Publication No. 7-154350, a center station adds an area code, such as a postal code, to specific multiplexed information when transmitting it through a broadcast medium. A receiving terminal, on the other hand, registers in advance the area code corresponding to an area that covers its current position in memory as the ID. In the terminal, a data extracting circuit separates multiplex information distributed from the center station to extract the area code added to the information. The terminal then compares the extracted area code with the ID registered in advance in the memory. If they match, the terminal enables the user to refer to the information with the area code added thereto.
As such, map providing systems for providing a terminal with cartographic data through telecommunications or broadcasting have been increasingly developed in recent years. In such map providing systems, the center station transmits cartographic data to the terminal, and the terminal receives the cartographic data and then stores it in a storage device. The stored cartographic data is used as required by users for carrying out viewing, route search, map matching, or other processing.
As described in the above first conventional art, the road network is conventionally represented by nodes and links, and the connection information among the nodes and the links is recorded in advance in the cartographic data. This is to quickly and efficiently read the connection information of the road network data in the cartographic data. However, the connection information among the nodes and the links recorded in the cartographic data is so detailed that the cartographic data becomes extremely large in amount.
Here, processing such as route search and map matching by using the cartographic data is briefly described. FIG. 11 is a schematic illustration showing example nodes and links represented by the cartographic data.
In FIG. 11, a road network represented in the cartographic data is composed of eight nodes N1 to N8 and twelve links L1 to L12. To carry out route search and map matching by using the road network, how the nodes and the links are connected has to be traced. For example, when the shortest route starting from the node N1 to the node N8 is traced as the node N1- greater than the link L2- greater than the node N3- greater than the link L6- greater than , the node N5- greater than the link L9- greater than the node N6- greater than the link L11- greater than the node N8, the route has to be traced as in the following processes.
Process 1: The node N1 has two links connected thereto, one of which is the link L2.
Process 2: The link L2 is connected to the node N3.
Process 3: The node N3 has five links connected thereto, one of which is the link L6.
Process 4: The link L6 is connected to the node N5.
Process 5: The node N5 has three links connected thereto, one of which is the link L9.
Process 6: The link L9 is connected to the node N6.
Process 7: The node N6 has four links connected thereto, one of which is the link L11.
Process 8: The link L11 is connected to the node N8.
In other words, the connection information has to include node-to-link information indicating which link is connected to each node (Processes 1, 3, 5, and 7) , and link-to-node information indicating which node is connected to each link (Processes 2, 4, 6, and 8).
Described next is road network data for tracing the route by using such connection information among the nodes and the links. FIG. 12 is an example structure of the road network data that represents the road network.
In FIG. 12, the road network data is structured by a node table that contains eight node records respectively corresponding the eight node N1 to N8, and a link table that contains twelve link records respectively corresponding the twelve links L1 to L12. Each node record in the node table stores data representing information about an attribute and coordinates of that node. Each node record also stores the number of links connected to that node, and link pointer information about a pointer indicating a storage location in the link table of each link record corresponding to the link connected to the node (the number of links and the link pointer information correspond to the node-to-link connection information described above).
On the other hand, each link record stores data representing information about an attribute of that link. Each link record also stores the number of nodes connected to the link, and node pointer information about a pointer indicating a storage location in the node table of each node record corresponding to the node connected to the link (the number of nodes and the node pointer information correspond to the link-to-node connection information described above).
With such data structure, it is possible to easily find which link is connected to an arbitrary node and further which node is connected to an arbitrary link, and therefore easily trace a route on the road network. In this data structure, however, each node record in the node table has to contain the link pointer information as many as the number of links connected to the node. Similarly, each link record in the link table has to contain the node pointer information for two nodes connected to the link. Consequently, information required for representing the road network data becomes enormous. The larger the area to be displayed based on the road network data (when the entire Japan is displayed, for example), the more the required data becomes increased in amount. Moreover, when a general-purpose information processing device having a small data storage capacity (a PDA, a cell phone terminal, etc.) is used, further reduction in the amount of the cartographic data is required.
Also in the map providing system described in the second conventional art, the cartographic data distributed from the center station to the terminal has the data structure as described above. Therefore, the cartographic data transmitted from the center station to the terminal becomes increased in amount, thereby increasing time and cost required for data transfer.
Therefore, an object of the present invention is to provide an information terminal and a cartographic information providing system capable of reducing the amount of digital cartographic data without impairing a function of an application using the cartographic data.
The present invention has the following features to attain the object above.
A first aspect of the present invention is directed to an information terminal for processing cartographic data including node data representing intersections on roads as nodes and link data representing the roads as links, and the terminal includes: a cartographic data storage section for storing the cartographic data; and a cartographic data processing section for processing the cartographic data stored in the cartographic data storage section. The cartographic data stored in the cartographic data storage section only has one-side connection information described therein, the one-side connection information indicating a connecting relation viewed in a direction from one of the nodes and the links to another one. The cartographic data processing section includes: a cartographic data reader for reading a required portion of the cartographic data from the cartographic data storage section; a complementing section for complementing the read cartographic data by generating another-side connection information based on the one-side connection information described in the cartographic data read by the cartographic data reader, the other-side connection information indicating a connecting relation viewed in a direction reverse to the direction taken in the one-side connection information; and a cartographic data arithmetic operation section for carrying out an arithmetic operation on the cartographic data complemented with the other-side connection in formation.
According to the above structure, the cartographic data stored in the cartographic data storage section has the one-side connection information indicating a connecting relation among nodes and links constructing the road network required for carrying out position detection, route search, etc., and the connecting relation is the one viewed either from the nodes to the links or from the links to the nodes. Therefore, it is possible to reduce the amount of cartographic data. As a result, the cartographic data storage section can store data covering a larger area or save its storage space. Also, based on the one-side connection information, the cartographic data processing section complements the cartographic data to be processed by newly generating the other-side connection information indicating a connecting relation viewed in a direction reverse to the direction taken in the one-side connection information. Therefore, it is possible to trace the connecting relation of the road network without impairing efficiency of processes such as position detection and route search using the cartographic data.
The cartographic data stored in the cartographic data storage section includes, in one example, node connection information indicating a connecting relation viewed from the links to the nodes as the one-side connect ion information. The complementing section complements the read cartographic data by generating, based on the node connection information included in the cartographic data read by the cartographic data reader, link connection information indicating a connecting relation viewed from the nodes to the links as the other-side connection information. In this case, of the information about connection among the nodes and links constructing the road network required for position detection, route search, etc., the cartographic data is so structured as to store only information about connection from the links to the nodes. In general, the information about connection from the nodes to the links is larger in amount than the information about connection from the links to the nodes. Therefore, the above structure is quite effective to reduce the amount of cartographic data. As a result, the cartographic data storage section can store data covering a larger area or save its storage space. Also, the cartographic data to be processed is complemented with a newly generated information about connection from the nodes to the links, the information that has been omitted. Therefore, it is possible to trace the connecting relation of the road network without impairing efficiency of processes such as position detection and route search using the cartographic data.
Also, the cartographic data stored in the cartographic data storage section includes, in another example, link connection information indicating a connecting relation viewed from the nodes to the links as the one-side connection information, and the complementing section complements the read cartographic data by generating, based on the link connection information included in the cartographic data read by the cartographic data reader, node connection information indicating a connecting relation viewed from the links to the nodes as the other-side connection information. In this case, of the information about connection among the nodes and links constructing the road network required for position detection, route search, etc., the cartographic data is so structured as to store only information about connection from the nodes to the links. Therefore, it is possible to reduce the amount of cartographic data. As a result, the cartographic data storage section can store data covering a larger area or save its storage space. Also, the cartographic data to be processed is complemented with a newly generated information about connection from the links to the nodes, the information that has been omitted. Therefore, it is possible to trace the connecting relation of the road network without impairing efficiency of processes such as position detection and route search using the cartographic data.
A second aspect of the present invention is directed to a cartographic information providing system in which an information terminal for processing cartographic data including node data representing intersections on roads as nodes and link data representing the roads as links is provided with the cartographic data from a center station via a transmission path. The center station includes: a first cartographic data storage section for storing the cartographic data; and a cartographic data transmitter for reading the cartographic data requested by the information terminal from the first cartographic data storage section and transmitting the read cartographic data to the information terminal via the transmission path. The information terminal includes: a cartographic data receiver for receiving the cartographic data transmitted from the center station via the transmission path; a second cartographic data storage section for storing the cartographic data received by the cartographic data receiver; and a cartographic data processing section for processing the cartographic data stored in the second cartographic data storage section. The cartographic data transmitted from the center station only has one-side connection information described therein, the one-side connection information indicating a connecting relation viewed in a direction from one of the nodes and the links to another one. The cartographic data processing section includes: a cartographic data reader for reading a required portion of the cartographic data from the cartographic data storage section; a complementing section for complementing the read cartographic data by generating another-side connection information based on the one-side connection information described in the cartographic data read by the cartographic data reader, the other-side connection information indicating a connecting relation viewed in a direction reverse to the direction taken in the one-side connection information; and a cartographic data arithmetic operation section for carrying out an arithmetic operation on the cartographic data complemented with the other-side connection information.
In the above structure, the cartographic data stored in the first cartographic data storage section includes information required for position detection, route search, etc., about a connecting relation among the nodes and links constructing the road network, but only includes the one-side connection information indicating a connecting relation viewed either from the links to the nodes or from the nodes to links as the oneside connection information. Therefore, it is possible to reduce the amount of cartographic data. As a result, the first cartographic data storage section can store data covering a larger area or save its storage space. Also, when the cartographic data stored in the first cartographic data storage section is transmitted from the center station to the information terminal via the transmission path, the data amount to be transmitted is small, thereby reducing time required for transmission. Furthermore, when the cartographic data transmitted via the transmission path is received by the information terminal for storage in the second cartographic data storage section, the data amount received is small, thereby enabling the second cartographic data storage section to store data covering a larger area or saving storage space of the second cartographic data storage section. Still further, the cartographic data processing section complements the cartographic data by generating, based on the one-side connection information, the other-side connection information indicating a connecting relation viewed in a direction reverse to the direction taken in the one-side connection information. Therefore, it is possible to trace the connecting relation of the road network without impairing efficiency of processes such as position detection and route search using the cartographic data.
The cartographic data transmitted from the center station includes, in one example, node connection information indicating a connecting relation viewed from the links to the nodes as the one-side connection information. The complementing section complements the read cartographic data by generating, based on the node connection information included in the cartographic data read by the cartographic data reader, link connection information indicating a connecting relation viewed from the nodes to the links as the other-side connection information. In this case, of the information about connection among the nodes and links constructing the road network required for position detection, route search, etc., the cartographic data stored in the first cartographic data storage section is so structured as to store only information about connection from the links to the nodes. In general, the information about connection from the nodes to the links is larger in amount than the information about connection from the links to the nodes. Therefore, the above structure is quite effective to reduce the amount of cartographic data. As a result, the first cartographic data storage section can store data covering a larger area or save its storage space. Also, when the cartographic data stored in the first cartographic data storage section is transmitted from the center station to the information terminal via the transmission path, the data to be transmitted is small, thereby reducing time required for transmission. Furthermore, when the cartographic data transmitted via the communication path is received by the information terminal for storage in the second cartographic data storage section, the received data amount is small, thereby enabling the second cartographic data storage section to store data covering a larger area or saving space in the second cartographic data storage section. Still further, the cartographic data to be processed is complemented with a newly generated information about connection from the nodes to the links, the information that has been omitted. Therefore, it is possible to trace the connecting relation of the road network without impairing efficiency of processes such as position detection and route search using the cartographic data.
Also, the cartographic data transmitted from the center station section includes, in another example, link connection information indicating a connecting relation viewed from the nodes to the links as the one-side connection information, and the complementing section complements the read cartographic data by generating, based on the link connection information included in the cartographic data read by the cartographic data reader, node connection information indicating a connecting relation viewed from the links to the nodes as the other-side connection information. In this case, of the information about connection among the nodes and links constructing the road network required for position detection, route search, etc., the cartographic data stored in the first cartographic data storage section is so structured as to store only information about connection from the nodes to the links. Therefore, it is possible to reduce the amount of cartographic data. As a result, the first cartographic data storage section can store data covering a larger area or save its storage space. Also, when the cartographic data stored in the first cartographic data storage section is transmitted from the center station to the information terminal via the transmission path, the data to be transmitted is small, thereby reducing time required for transmission. Furthermore, when the cartographic data transmitted via the communication path is received by the information terminal for storage in the second cartographic data storage section, the received data amount is small, thereby enabling the second cartographic data storage section to store data covering a larger area or saving space in the second cartographic data storage section. Still further, the cartographic data to be processed is complemented with a newly generated information about connection from the links to the nodes, the information that has been omitted. Therefore, it is possible to trace the connecting relation of the road network without impairing efficiency of processes such as position detection and route search using the cartographic data.
A third aspect of the present invention is directed to a computer program embodied on a computer readable medium for processing cartographic data including node data representing intersections on roads as nodes and link data representing the roads as links. The program includes: a step storing the cartographic data; and a step of processing the cartographic data stored in the storing step. The cartographic data stored in the storing step only has one-side connection information described therein, the one-side connection information indicating a connecting relation viewed in a direction from one of the nodes and the links to another one. The cartographic data processing step includes: a step of reading a required portion of the cartographic data stored in the storing step; a step of complementing the read cartographic data by generating another-side connection information based on the one-side connection information described in the cartographic data read by the reading step, the other-side connection information indicating a connecting relation viewed in a direction reverse to the direction taken in the one-side connection information; and a step of carrying out an arithmetic operation on the cartographic data complemented with the other-side connection information
The cartographic data stored in the storing step includes, in one example, node connection information indicating a connecting relation viewed from the links to the nodes as the one-side connection information. In the complementing step, the read cartographic data is complemented with link connection information indicating a connecting relation viewed from the nodes to the links as the other-side connection information, the link connection information generated based on the node connection information included in the cartographic data read in the reading step. Also, the cartographic data stored in the storing step includes link connection information indicating a connecting relation viewed from the nodes to the links as the one-side connection information. In the complementing step, the read cartographic data is complemented with node connection information indicating a connecting relation viewed from the links to the nodes as the other-side connection information, the node connection information generated based on the link connection information included in the cartographic data read in the reading step.
A fourth aspect of the present invention is directed to a computer program embodied on a computer readable medium for processing cartographic data including node data representing intersections on roads as nodes and link data representing the roads as links, the cartographic data being provided by a center station via a transmission path. The program includes: a step of receiving the cartographic data from the center station via the transmission path; a step of storing the cartographic data received in the receiving step; and a step of processing the cartographic data stored in the storing step. The cartographic data stored in the storing step only has one-side connection information described therein, the one-side connection information indicating a connecting relation viewed in a direction from one of the nodes and the links to another one. The cartographic data processing step includes: a step of reading a required portion of the cartographic data stored in the storing step; a step of complementing the read cartographic data by generating another-side connection information based on the one-side connection information described in the cartographic data read by the reading step, the other-side connection information indicating a connecting relation viewed in a direction reverse to the direction taken in the one-side connection information; and a step of carrying out an arithmetic operation on the cartographic data complemented with the other-side connection information.
The cartographic data transmitted from the center station includes, in one example node connection information indicating a connecting relation viewed from the links to the nodes as the one-side connection information. In the complementing step, the read cartographic data is complemented with link connection information indicating a connecting relation viewed from the nodes to the links as the other-side connection information, the link connection information generated based on the node connection information included in the cartographic data read in the reading step. Also, the cartographic data transmitted from the center station includes, in another example, link connection information indicating a connecting relation viewed from the nodes to the links as the one-side connection information. In the complementing step, the read cartographic data is complemented with node connection information indicating a connecting relation viewed from the links to the nodes as the other-side connection information, the node information generated based on the link connection information included in the cartographic data read in the reading step.
A fifth aspect of the present invention is directed to an information processing method for processing cartographic data including node data representing intersections on roads as nodes and link data representing the roads as links. The method includes: a step of storing the cartographic data; and a step of processing the cartographic data stored in the storing step. The cartographic data stored in the storing step only has one-side connection information described therein, the one-side connection information indicating a connecting relation viewed in a direction from one of the nodes and the links to another one. The cartographic data processing step includes: a step of reading a required portion of the cartographic data stored in the storing step; a step of complementing the read cartographic data by generating another-side connection information based on the one-side connection information described in the cartographic data read by the reading step, the other-side connection information indicating a connecting relation viewed in a direction reverse to the direction taken in the one-side connection information; and a step of carrying out an arithmetic operation on the cartographic data complemented with the other-side connection information.
The cartographic data stored in the storing step includes, in one example, node connection information indicating a connecting relation viewed from the links to the nodes as the one-side connection information. In the complementing step, the read cartographic data is complemented with link connection information indicating a connecting relation viewed from the nodes to the links as the other-side connection information, the link connection information generated based on the node connection information included in the cartographic data read in the reading step. The cartographic data stored in the storing step includes, in another example, link connection information indicating a connecting relation viewed from the nodes to the links as the one-side connection information. In the complementing step, the read cartographic data is complemented with node connection information indicating a connecting relation viewed from the links to the nodes as the other-side connection information, the node connection information generated based on the link connection information included in the cartographic data read in the reading step.
A sixth aspect of the present invention id directed to a cartographic information providing method for providing an information terminal with cartographic data including node data representing intersections on roads as nodes and link data representing the roads as links, the cartographic data being provided by a center station via a transmission path. The method includes, at the center station, the method comprising, at the center station, a first storing step of storing the cartographic data; and a step of reading a portion of the cartographic data requested by the information terminal from the cartographic data stored in the first storing step, and transmitting the read cartographic data to the information terminal via the transmission path; and at the information terminal device, a step of receiving the cartographic data transmitted from the center station via the transmission path; a second storing step of storing the cartographic data received in the receiving step; and a step for processing the cartographic data stored in the second storing step. The cartographic data transmitted from the center station only having one-side connection information described therein, the one-side connection information indicating a connecting relation viewed in a direction from one of the nodes and the links to another one. The cartographic data processing step includes: a step of reading a required portion of the cartographic data stored in the second storing step; a step of complementing the read cartographic data by generating another-side connection information based on the one-side connection information described in the cartographic data read by the reading step, the other-side connection information indicating a connecting relation viewed in a direction reverse to the direction taken in the one-side connection information; and a step of carrying out an arithmetic operation on the cartographic data complemented with the other-side connection information.
The cartographic data transmitted from the center station includes, in one example, node connection information indicating a connecting relation viewed from the links to the nodes as the one-side connection information. In the complementing step, the read cartographic data is complemented with link connection information indicating a connecting relation viewed from the nodes to the links as the other-side connection information, the link connection information generated based on the node connection information included in the cartographic data read in the reading step. The cartographic data transmitted from the center station includes, in another example, link connection information indicating a connecting relation viewed from the nodes to the links as the one-side connection information. In the complementing step, the read cartographic data is complemented with node connection information indicating a connecting relation viewed from the links to the nodes as the other-side connection information, the node information generated based on the link connection information included in the cartographic data read in the reading step.
These and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.